N-vinylamides have long been used as monomers for the production of homopolymers and copolymers having valuable properties. The polymer resulting from the polymerization of N-vinylamide contains reactive hydrogens which can be used as sites for effecting crosslinking attachment of activated substrates onto the polymer or the amide may be hydrolyzed to form polyvinylamine which is suitable for other uses.
Parris, et al. in U.S. Pat. No. 4,942,259 disclose catalytic processes for the cracking of N-(alkoxyalkyl)formamides and N-(alkoxyalkyl)amides as well as the corresponding bit-amides to produce the corresponding N-alkenyl amides. The N-alkenyl amides then can be polymerized. Of these, it is the N-(1-alkoxyethyl)formamides and bisformamides that lend themselves to the Parris, et al. catalytic cracking process to form N-vinylformamide; also it is the polymers formed from N-vinylformamide which can be more easily hydrolyzed than the polymers formed from an N-alkenylamide.
A number of routes for producing N-vinylcarboxylic amides have been suggested and these routes generally involve the production of either N-(alpha-alkoxyethyl)amides alternatively referred to as N-(1-alkoxyethyl)carboxylic acid amides. Representative patents and articles which illustrate preparation of N-vinylamides are as follows: Stackman in U.S. Pat. No. 4,554,377 and in an article entitled Synthesis of N-vinylacetamide and Preparation of Some Polymers and Copolymers, 24 Ind. Eng. Chem. Prod. Res. Dev., 242-246 (1985), disclose the reaction of acetamide with dimethyl acetal to form the N-(alpha-alkoxyethyl)carboxylic acid amide. In this reaction there is a competing equilibrium reaction and this reaction involves the subsequent reaction of the N-(alpha-alkoxyethyl)carboxamide with another mole of alkylamide to form ethylidene-bis(alkylamide), an unwanted co-product. The reaction is carried out in the presence of an acid, such as methanesulfonic acid or sulfuric acid. When formamide was substituted for acetamide, the reaction was unsuccessful (p. 244).
Schmidt U.S. Pat. No. 4,334,097 discloses a process for producing N-(alpha-alkoxyalkyl)carboxamides by reacting primary and secondary carboxamides with an alpha-halogen alkyl ether. Tertiary amines are added to the reaction system to react with hydrogen halide as it is formed. The tertiary amine hydrogen halide then can be filtered from the reaction product and removed.
Bestian in German Patent 1,273,533 discloses a process for producing N-(alpha-alkoxyalkyl)carboxylic acid amides by reacting a secondary amide with acetals or hemiacetals. Representative acetals include those formed by the reaction of an aldehyde with primary and secondary alcohols, e.g., methanol, ethanol, isopropanol, and isobutanol. Acid catalysts including inorganic acids, such as, hydrochloric acid, acid chlorides, such as, sulfuryl chloride, and aromatic sulfonic acids and acid chlorides, such as, p-toluenesulfonic acid and chloride thereof are suggested as being suited for effecting reaction between the secondary carboxylic acid amide and acetal or hemiacetal.
N-(1-alkoxyethyl)carboxylic acid amides have been prepared by the electrochemical alkoxylation of N-ethylcarboxylic acid amides and by the reaction of formamide with aldehydes. In this regard Murao, et al. disclose in U.S. Pat. No. 4,567,300 and equivalent GB 2 152 929 a process wherein acetaldehyde reacts with formamide in the presence of a weakly basic catalyst to yield solid N-(1-hydroxyethyl)formamide which, following catalyst neutralization, reacts with alcohols in the presence of an acid catalyst to yield N-(1-alkoxyethyl)formamide. This process is unattractive in that it requires two discrete steps, the handling of a solid intermediate and the disposal of salts.
European Patent Publication 0 332,083 discloses the preparation of N-(1-alkoxyalkyl)carboxylic acid amides by reacting formamide with acetals derived from primary alcohols to produce the N-(1-alkoxyalkyl)formamide systems along with bisformamide. This reaction, in contrast to the statements made by Stackman, et al., is successful but requires the utilization of large amounts of acid in order to force the reaction of formamide with the acetal of a primary alcohol to form the N-(1-alkoxyalkyl)formamide.